Why does the liquid rise up through the dip tube when the valve is opened? The propellant gas wants to expand as much as it can, so if the valve is open, the propellant expands and pushes the spray up out of the can making more room for itself to expand.
The liquid spray wants to expand as much as it can, so when the valve is opened, it naturally moves up through the tube, leaving behind the propellant gas that was holding it back.
The compressed gas is able to reverse the force of gravity because gravity does not work on atoms that are far apart. So when the force is reversed, the spray moves up instead of down.
The valve allows air into the can, and since air is expandable, it comes into the can and pushes out the propellant and spray that had been in the can before.